Now that 2007 mandates for diesel engines have been fully-implemented, the Environmental Protection Agency is gearing up to enforce new diesel exhaust regulations that take effect in 2010. The new regulations will dramatically reduce discharges of both particulate matter (soot and ash), hydrocarbons and nitrogen oxide.
   EPA’s goal for 2010 is to reduce NOx emissions to 0.2 grams per brake horsepower-hour, or about 90% of pre-2004 levels. Meeting the reduced pollutant standards has required a change in diesel fuel to ultra-low sulfur diesel fuel, a cleaner-burning fuel that produces less particulate emissions from combustion. The standards have also required a reformulation of engine oils, called CJ-4 or low-ash oils, which are designed with better wear protection, higher oxidation protection and better soot handling characteristics. 
   In addition, manufacturers are making engine modifications for cleaner combustion and adding exhaust after treatment devices to remove pollutants from exhaust gases after they leave the engine’s combustion chamber. These include selective catalytic reduction and exhaust gas recirculation technologies to control NOx emissions, as well as diesel particulate filter technology to handle particulate matter emissions. 
   SCR is a system that works by a chemical reaction triggered by heat. It treats the downstream exhaust by injecting a fine mist of diesel exhaust fluid into the exhaust gas. DEF, also known as urea, is an organic compound that is harmless to the environment and commonly distributed for a wide range of industrial and agricultural purposes. Consumption of urea varies but a common rule of thumb is that 1 gallon of urea will take a truck about 250 miles. 
   Both EGR and SCR are proven technologies that have been used in a wide range of applications around the world to meet emission requirements for diesel-powered commercial vehicles. An article published in June 2009 in Light & Medium Truck magazine, states that “Most light-duty and medium-duty commercial trucks will use SCR to control diesel emissions…. [and] SCR-equipped trucks also will require some training for drivers and technicians.”
   According to the EPA, reducing emissions from diesel engines is one of the most important air quality challenges facing the nation today. As a result, as part of the American Recovery and Reinvestment Act of 2009, which includes $300 million to support clean diesel activities, the EPA has awarded $86.5 million for clean diesel activities to 49 states and the District of Columbia through its National Clean Diesel Campaign. 
   Truck and engine manufacturers that have announced that they will offer SCR to meet EPA 2010 diesel emissions standards include: Daimler Trucks North America (Freightliner, Western Star), Detroit Diesel Corporation, Cummins Engines, Volvo Trucks North America (Volvo, Mack) and PACCAR (Peterbilt, Kenworth). Light and medium duty truck and equipment producers planning to use SCR for 2010 include Hino Motors and Isuzu. Passenger vehicles including Audi, BMW, Hyundai, Jeep, Kia, Mercedes-Benz, Mini and Volkswagen currently offer SCR emission control technologies.
   For some businesses, making a choice between diesel and gasoline engines continues to be a challenge. Benefits of gasoline engines include lower cost, better access and lower price fuel, quieter operations, easier maintenance and faster cab heater warm-up. On the other hand, diesel engines have advantages such as better fuel economy, greater warranty period coverage and higher resale value, as well as fewer tune-ups and longer maintenance intervals. 
   While there clearly are positive and negative attributes of each engine, the most important consideration is to analyze how vehicles will be used.